Re: [PATCH rfc 0/5] mm: introduce shrinker sysfs interface

[Mike Rapoport <rppt@kernel.org>]

On Fri, Apr 15, 2022 at 05:27:51PM -0700, Roman Gushchin wrote:
> There are 50+ different shrinkers in the kernel, many with their own bells and
> whistles. Under the memory pressure the kernel applies some pressure on each of
> them in the order of which they were created/registered in the system. Some
> of them can contain only few objects, some can be quite large. Some can be
> effective at reclaiming memory, some not.
> 
> The only existing debugging mechanism is a couple of tracepoints in
> do_shrink_slab(): mm_shrink_slab_start and mm_shrink_slab_end. They aren't
> covering everything though: shrinkers which report 0 objects will never show up,
> there is no support for memcg-aware shrinkers. Shrinkers are identified by their
> scan function, which is not always enough (e.g. hard to guess which super
> block's shrinker it is having only "super_cache_scan"). They are a passive
> mechanism: there is no way to call into counting and scanning of an individual
> shrinker and profile it.
> 
> To provide a better visibility and debug options for memory shrinkers
> this patchset introduces a /sys/kernel/shrinker interface, to some extent
> similar to /sys/kernel/slab.

Wouldn't debugfs better fit the purpose of shrinker debugging?
 
-- 
Sincerely yours,
Mike.